One of the most useful hot-key commands in Firefox is Ctrl+Tab. Unlike the Alt+Tab hot-key combo for Windows, which lets you jump from program to program in an interface based on the program's icon, the browsing tab switcher has never had a graphic interface--until now.
In this CNET TV Quick Tip, Molly Wood shows you the new tab switching GUI (graphical user interface) that's coming in Firefox 3.1. It's only in beta now, so if you're not comfortable installing unstable software, I recommend holding off for the official release.
After playing around with the feature a few weeks ago, all I can add is this: what on Earth took Mozilla so long?